This study is designed to explore alterations in metabolic demand which sarcomas imposed on patients. Since soft-tissue sarcomas have been shown to be metabolically active tumors and NCI is treating a large number of patients with extremity and truncal sarcomas this study will be limited to sarcoma patients. Of particular interest is the followin: 1. Is there any alteration in resting energy expenditure due to the presence of the tumor? 2. Is there any alteration in body cell mass prior to the onset of cachexia? Previous studies have been limited to very sick patients or small numbers of patients. This study will attempt to further our understanding of the pathophysiology of covert cachexia before it becomes clinically evident. Patients and volunteers will be matched with respect to age, sex, and body surface area.